When carrying out radio communication using a power transmitting coil, use of a load modulation scheme or backscattering scheme is assumed which enables non-electric source driving used for RFID (Radio Frequency IDentification) or the like. When performing backscattering in the conventional RFID, the modulation scheme or frequency is made variable depending on coupling between coils.
However, when the above-described prior art is applied to magnetic resonance type radio power transmission, since transmission characteristics cannot be ascertained when information transmission starts, signals obtained by load modulation or backscattering may significantly attenuate.